It is often desired to change the density of scanning lines in a single magnetic printing apparatus. For instance, records are usually obtained at a density of 10 scanning lines per millimeter. When it is desired to obtain a more finely printed copy, the density is increased to, for example, 13 scanning lines per millimeter. In a facsimile, on the other hand, the density of 4 scanning lines per millimeter or 8 scanning lines per millimeter will suffice. In a composite apparatus, furthermore, the density of 10 scanning lines per millimeter is selected when it is used as a printer, or the density of 13 scanning lines per millimeter is selected when it is used as a copying machine. It is not advantageous to provide recording heads in a number corresponding to the number of scanning line densities. A recording system that meets such a requirement was already disclosed in Japanese Patent Publication No. 32,340/79 which was filed by one of the inventors of this invention.
In this prior art, there is only one recording head, having a core the width of which is larger than the distance between the scanning lines, and the scanning is carried out by changing the speed, so that the width of the core overlaps the scanning lines by the amount of the difference between the core width and the distance between the scanning lines.
However, in the prior art, the apparatus cannot be operated with sufficient efficiency.